1. Field of the Invention
This invention relates to a blood reservoir for use in an extracorporeal blood circulation circuit with an artificial lung, the reservoir having a blood accumulating/delivering means for temporarily storing blood and delivering the once stored blood. It also relates to a blood delivery instrument and blood delivery apparatus for use in an extracorporeal blood circulation circuit including a blood tank, the instrument and apparatus being disposed downstream of the tank for delivering blood to a downstream destation.
2. Prior Art
Heart surgery often uses an extracorporeal blood circulation circuit having incorporated therein an artificial lung for removing carbon dioxide from blood and adding oxygen to blood instead of the living lung. The extracorporeal circulation circuit is to drain blood from the patient's vein, subject the blood to gas exchange in the artificial lung, and return the blood to the patient's artery. The extracorporeal circulation circuit also includes a cardiotomy line for sucking in blood from the operation area, removing foreign matter therefrom, and returning the blood.
In general, the exacorporead circulation circuit with an artificial lung includes a blood tank for temporarily storing blood drained from the patient and a cardiotomy reservoir for filtering blood sucked from the operation area and temporarily storing the blood. The blood tank and cardiotomy reservoir serve a buffering function of adjusting the amount of blood in the circuit and maintaining a constant amount of blood returned to the patient.
There is a situation that the volume of blood in the blood tank becomes zero during extracorporeal blood circulation. If the blood feed pump continues to operate, air can be fed into the extracorporeal circulation circuit. To avoid such inconvenience, the tank is provided with a level sensor for monitoring the volume of blood in the tank. When the sensor detects that the volume of blood in the tank is below a predetermined value, the feed pump is interrupted to stop blood delivery action until the volume of blood in the blood tank is restored. The temporary interruption of blood delivery, however, is undesirable because it causes blood stagnation throughout the circuit including the artificial lung.
Therefore, an object of the present invention is to provide a blood reservoir, blood delivery instrument and blood delivery apparatus which can regulate the amount of blood delivered in accordance with the volume of blood in the blood tank when the volume of blood in the blood tank is reduced below a predetermined value.